While her fellow MoMusu are busy with more mundane interests, our Sayumi is off challenging herself with math problems (here, Sayu, try Project Euler) and has apparently discovered the wonders of linear algebra (I’m assuming at least some of those simultaneous equations are linear). No doubt Sayumi has mastered the techniques of Gauss-Jordan elimination, Cramer’s rule, and LU decomposition and is well on her way to achieving world domination.